1. Field of the Invention
This invention relates to grinding machines and, in particular, to a small, lightweight grinding wheel spindle assembly.
2. Description of the Prior Art
A conventional grinding wheel spindle assembly, as shown in FIG. 5, comprises a cylindrical-shaped rotating shaft 52 supported by bearings 51,51 within a housing 50, a grindstone (grinder) 54 mounted on one end of the rotating shaft 52 for relative rotation therewith through a flange 53, a pulley 56 provided on the other end of the rotating shaft 52, and a driving motor 55 coupling with the pulley 56 through a belt 57 and a motor pulley 58. The grindstone 54 is rotated together with the rotating shaft 52 which is driven by the driving motor 55 through the motor belt 58, belt 57 and pulley 56.
In the foregoing conventional grinding wheel assembly, the grindstone 54 is mounted on one end of the rotating shaft 52 for relative rotation therewith through the flange 53. The grindstone 54 and the flange 53 are mounted together as one unit and are sequentially arranged on an extended axis of the rotating shaft 52. Thus the length of the rotating shaft 52 is extended by a length corresponding to those of the grindstone 54 and the flange 53. Additionally, because the grindstone 54 and the flange 53 are arranged on one end of the rotating shaft 52, a greater thickness and larger diameter is required for the cylindrical-shaped rotating shaft 52 for maintaining a required rigidity thereof. Hence, a larger size housing 50 is required to house the rotating shaft 52 and the supporting members of the bearings 51,51 supporting the rotating shaft 52. Consequently, such conventional grinding wheel spindle assembly is relatively heavy and have rather large components which do not permit the assembly to be of reduced scale.
Moreover, in order to reduce a contact pressure between the relatively large and heavy grinding wheel spindle assembly, such as a depth-cutting motion unit, and a guide of a depth-cutting transfer structure, for depth-cutting of the depth-cutting motion unit, and to allow smooth relative sliding between the unit and the guide, a guiding surface of the guide is required to be formed wider is size and the driving motor selected for the unit must be larger. Such large and heavy grinding machine thus provided by the conventional art suffers from the drawback that it is unable to fine depth-cut with precision.